This invention relates to a lift assist system for a tailgate of a vehicle, such as a pickup truck or sport utility vehicle.
A tailgate for a vehicle, such as a pickup truck or sport utility vehicle, is typically hinged to a vehicle support or frame member and may be opened and closed by pivoting the tailgate about its hinge to facilitate access to a truck bed or passenger compartment. A tailgate may be very heavy, particularly in the case of sport utility vehicles, because window lift and position control components are often housed within the tailgate. As a consequence, some assistance may be necessary to open and close the tailgate.
Systems do exist that provide lift assistance for the tailgate of the vehicle. Indeed, several known systems employ springs to counterbalance the weight of the tailgate. These springs are located in the sidewalls of the bed of the vehicle. One such system attaches one end of a cable to a spring in the sidewall of the vehicle and the other end to the tailgate. When the tailgate is lowered, the spring expands. Lift assistance to the tailgate is then provided by the returning spring as the tailgate is lifted.
Such a system, however, has several drawbacks. The spring force must be closely balanced with the weight of the tailgate so that a vehicle occupant may easily close the tailgate. However, as a consequence, very little upward lift may cause the tailgate to close quickly.
In addition, a driver of the vehicle may desire to keep the tailgate open during vehicle operation, so as to accommodate oversized loads that may extend beyond the vehicle bed or to allow loading or unloading of the vehicle while moving. Due to the counterbalancing effect of the spring, over rough roads, the tailgate may close when the driver prefers it to remain open. The tailgate may also bounce up and down on these roads more so than without the lift assistance. A fluctuating tailgate places stress on the tailgate hinge as well as the lift assist system.
Moreover, it is very difficult to install the spring in the sidewall during vehicle production. Specifically, the spring must be mounted to the sidewall during assembly of the vehicle body, which is difficult to access because the sidewalls typically form an integral part of the body. Sidewalls for a sport utility vehicle are especially difficult to access because of the integration of the sidewalls with a vehicle roof. Installing a spring inside the sidewall accordingly interferes with the assembly of the vehicle body.
Another option would be to install the assist spring outside the sidewall, which avoids interruption of body assembly. However, the spring is then open to the environment and more susceptible to wear and damage. Thus, it is preferable to keep the spring housed and protected.
Another disadvantage with existing systems is that when the tailgate is opened, the weight of the tailgate is supported in part by the compressed spring. This design places significant stress on the spring and housing for the spring and requires significant reinforcement. As a result, installation of the lift system is time consuming and expensive.
A need therefore exists for a tailgate assembly that incorporates a lift assist system without the drawbacks encountered by existing systems.